Low-temperature synthesis of cements from rice hull ash

Rice hull is an agricultural by-product containing about 20% of silica. Usually, this material is burned at the rice fields generating small silica particles, which may cause respiratory and environmental damage. This work describes the use of rice hull ash as a raw material to prepare Ca₂SiO₄-related cements, which is a component of commercial Portland cement. Rice hull was heated at 600 °C rendering silica with a surface area of 21 m² g⁻¹. This material was mixed with CaO and BaCl₂·2H₂O in several proportions, added stoichiometricaly in order to keep a ratio (Ca+Ba)/Si=2. The solids were mixed with water 1:20 (w/w) and sonicated for 60 min. The suspensions were dried and heated at several temperatures (from 500 to 1100 °C). The resulting solids were analyzed by FT-IR spectroscopy and X-ray diffraction. Cements with structure similar to that of β-Ca₂SiO₄ were obtained at temperatures as low as 700 °C, according to the composition.     

膜技术在医药生产中的应用

通过膜过程分类及其分离机理的介绍,论述了膜技术在医药生产中的应用及膜分离系统选用应注意的问题。阐述了膜分离技术在医药生产中的重要性及未来的发展前景。     

Context-aware cognitive design assistant: Implementation and study of design rules recommendations

Design rules are an essential interface to facilitate the information exchange between designers and experts. Despite many innovations in Knowledge-Based Engineering and Knowledge Management, unstructured design rules documents are still widely used in the manufacturing industry. Due to the complexity of the design process, these documents often contain hundreds of design rules, applicable in varying design contexts. Searching for the right rules according to a design context is demanding in time and cognitive resources. In this paper, we propose a Context-Aware Cognitive Design Assistant (CACDA) to capture the design context and perform tasks such as the recommendation of design rules, the verification of design solutions, or the automation of design routines. Contrary to existing works in model quality testing, the CACDA uses a proactive approach of design rules application and helps designers to provide error-free designs on first attempt. In this paper, we present the design rules recommendation system of the CACDA, its capabilities and its implementation. Then, to measure the impact of design rules recommendations on the design process, we compare our approach with the use of traditional design rules documents. Results show that the use of the CACDA’s design rules recommendations lower the perceived difficulty of design rules retrieval from 75 to 43.5 on a scale of 100. On average, participants that used the demonstrator successfully applied 8.6 design rules on the 25 applicable design rules of our set. Participants that used unstructured documentation correctly applied 4.3 design rules. The global cognitive weight of the design activity as well as the design rules retrieval performances appear to be unchanged. These results demonstrate the usability of the demonstrator and show a positive impact on the design process and on the quality of CAD models. Future works will focus on the overcome of the main limitations of our current experiments, with a panel of professional designers, a lager design rules set and the implementation of several lacking features of the CACDA into the demonstrator.     

制造误差的灰自助动态预报

综合考虑灰色系统理论和Bootstrap统计理论的信息预报特点,建立制造误差的灰自助动态预报模型GBM(1,1),以解决信息预报中存在的一些问题。GBM(1,1) 在灰微分建模时进行Bootstrap再抽样,更多地挖掘系统信息,从而更准确地预报系统真值及其分布区间的瞬态变化状况。在计算机仿真中,研究了各种随机误差系统例如正态分布、瑞利分布、均匀分布、三角分布以及混合分布等系统的预报问题,也涉及到一些系统误差例如上升趋势、下降趋势和周期趋势等误差的预报问题。在实际试验中,研究了滚动轴承套圈磨削圆度误差的预报问题。计算机仿真和试验研究表明,GBM(1,1)允许小的数据样本以及各种类型的随机误差与系统误差存在,预报的准确率可以达到95%以上。     

定子无磁轭模块化轴向磁通永磁电机研究进展综述

定子无磁轭模块化(yokeless and segmented armature,YASA)轴向磁通永磁电机具有功率密度和转矩密度高、效率高、轴向结构紧凑、易于维修的优点,在电动汽车、风力发电等领域有广阔的应用前景,已有大量文献对YASA电机进行分析研究。该文基于国内外对YASA电机已开展的研究工作,介绍该类电机的典型拓扑结构,并从电机电磁特性计算方法与性能优化、损耗分析与抑制技术、温升与散热研究、齿槽转矩削弱技术、结构强度校核与制造偏差分析,以及定子铁心材料选取等方面进行综述,并对该类电机当前的应用情况进行整理。最后,基于YASA电机的研究现状,对未来研究的发展趋势进行展望。     

多点成形数值模拟中的基本体成形曲面造型方法

基本体群成形面曲面造型是多点成形数值模拟中的关键问题之一。本文给出了基本体群成形面造型方法，并开发了相关程序。在此基础上，对多点成形中球面件的起皱缺陷及马鞍面的成形力进行了数值分析。     

带内筋筒形件强力旋压成形试验研究

通过选取不同的壁厚减薄率和旋轮进给比作为工艺参数，利用双旋轮强力旋压机对带内筋筒形件作旋压加工实验。根据实验结果分析了各种生产缺陷产生的原因，并提出了一定的解决办法，从而为减少大规模生产的经济损失，生产出合格的工件提供了理论和实践依据。     

5182铝合金板温成形工艺及摩擦学特性的研究

通过对5182铝合金板的室温及高温力学性能的实验研究与分析，提出了5182铝板的温成形工艺。实验研究了工艺参数对5182可成形性能的影响，并分析了成形过程中材料表面化学性能、表面几何形貌和润滑状态等因素对摩擦学特性的影响，最后进行了仿车门零件的成形实验和有限元模拟。     

中小型圆锥轴承套圈塔锻工艺分析

在分析国内外轴承套圈毛坯锻造工艺的基础上，介绍了轴承套圈塔锻工艺及其特点。     

大直径无心磨金刚石砂轮制作及修整工艺研究

大直径无心磨砂轮（一般指直径D≥500mm，厚度H≥150mm）制造工艺一直是难点，具体表现在制造过程成品率低，性能难以满足要求。本文对大直径无心磨金刚石砂轮的制造工艺进行分析和讨论，提出一套完整可行制造工艺，具体包括：通过采用梯度粒度提高粗糙度，改进工艺配方提高自锐性，对实际制造过程中注意问题进行较全面分析以提高制造成品率，并对大直径无心磨金刚石砂轮热压机常用工艺热压参数热压级功率、吨位、加热板面积等进行讨论，得出合理热压工艺参数；最后，对修整工艺进行研究，大直径无心磨金刚石砂轮对修整要求精度高而且操作困难。笔者在T8365型制动鼓镗床设计全新修整工艺，实际应用证明修整工艺可操作性强，修整精度高。